The leash-system works as follows: its makes a difference in the line lenghts. This difference has to minimal as long as the span of your kite. So for exaple the rhino 12 has a span of 10m, so you have to create a difference in line lengths of 10m. If you're leash is connected 5 m from the bar at one of the leader-lines the difference will be 2 times this length = 10m.
Hope you understand it, it's hard to explain and my english is not so well